Compared to conventional liquid crystal panels, an Active Matrix Organic Light Emitting Diode (AMOLED) panel has characteristics such as a faster response speed, a higher contrast, and a wider view angle and the like. Thus, AMOLED has gained an increasing attention of developers of display devices.
The AMOLED is driven via a pixel circuit to emit light. A conventional 2T1C pixel circuit comprises two Thin Film Transistors (TFTs) and one capacitor (C), and is particularly illustrated in FIG. 1, the pixel circuit comprises a driving transistor DTFT, a switching transistor T5′ and a storage capacitor Cst, wherein the switching transistor T5′ is controlled by a scan signal Vscan to control an input of a data voltage Vdata, the driving transistor DTFT controls an OLED to emit light, and the storage capacitor Cst supplies a maintaining voltage to a gate of the driving transistor DTFT.
FIG. 2 shows a driving timing diagram of the 2T1C pixel circuit illustrated in FIG. 1. The operational process of the 2T1C pixel circuit is as follows: when the scan signal is at a low level, the switching transistor T5′ is turned on, and the storage capacitor Cst is charged by a grayscale voltage (a data voltage Vdata) on a data line; meanwhile, the data voltage Vdata is applied to the gate of the driving transistor DTFT, so that the driving transistor DTFT operates in a saturation state to drive the OLED to emit light; when the scan signal is at a high level, the switching transistor T5′ is turned off, and the storage capacitor Cst supplies the maintaining voltage to the gate of the driving transistor DTFT, so that the driving transistor DTFT still operates in a saturation state to drive the OLED to emit light continuously.
It can be known from the above, the OLED in the AMOLED panel can be driven to emit light by a driving current generated by the driving transistor DTFT in the saturation state. Specifically, the driving current (flowing through an circuit in which OLED is located) IOLED=K(Vsg−|Vthd|)2, wherein Vsg represents a voltage difference between the gate and a source of the driving transistor DTFT, |Vthd| represents a threshold voltage of the driving transistor DTFT, K represents a constant concerning the structure and technical process of the driving transistor DTFT itself. Since in an existing low temperature poly-silicon manufacturing process, the uniformity of the threshold voltages Vth of TFTs is poor, and the threshold voltages may drift in operation, and thus even if a same data voltage Vdata is input to the respective driving transistors DTFT, different driving currents are generated due to different threshold voltages of the driving transistors DTFT, so that the uniformity of the luminance of the AMOLED panel is poor.
In recent years, a touch function is widely used in various display panels especially in mobile displays, and nearly becomes a standard configuration of a smart phone. In the prior art, a display panel and a Touch Screen Panel (TSP) are manufactured separately, and then are bonded together. Such a technical process flow brings about a complex technical process and high cost of a functional panel in a display touch panel, and has adversely affected the lightness and thinness of the displays. The technique of TSP in cell integrates the display function with the touch function, and can utilize one technical process flow rather than two separate technical flows to realize the combination of the display function and the touch function. Therefore, the technique of TSP in cell not only has an advantage of low cost, but also brings about a simple technical process, and results in a lighter and thinner display touch panel. However, at present, there is no a better solution to the problem how to integrate a touch circuit with a pixel circuit perfectly.